Use multi-echo fMRI protocol

[tsalo]

1. Take the fMRI scan from Satterthwaite/MEBOLD_ABCD_COMPARE/DCAN:func_run-01_task-rest_acq-multiecho
2. Take the field maps from Satterthwaite/MEBOLD_ABCD_COMPARE/DCAN:fmap_dir-[PA|AP]_acq-MESE, but modify:
   • Drop all but the first echo.
   • Enable magnitude+phase reconstruction or disable Maxwell correction, as magnitude+phase reconstruction automatically disables Maxwell correction and this will cause a slight mismatch between the fMRI scan's distortion and the field maps' distortion.
3. Rename frackack task to fracback.